xref: /openbmc/linux/arch/powerpc/kernel/watchdog.c (revision 8cb5d748) 
1 /*
2  * Watchdog support on powerpc systems.
3  *
4  * Copyright 2017, IBM Corporation.
5  *
6  * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c
7  */
8 #include <linux/kernel.h>
9 #include <linux/param.h>
10 #include <linux/init.h>
11 #include <linux/percpu.h>
12 #include <linux/cpu.h>
13 #include <linux/nmi.h>
14 #include <linux/module.h>
15 #include <linux/export.h>
16 #include <linux/kprobes.h>
17 #include <linux/hardirq.h>
18 #include <linux/reboot.h>
19 #include <linux/slab.h>
20 #include <linux/kdebug.h>
21 #include <linux/sched/debug.h>
22 #include <linux/delay.h>
23 #include <linux/smp.h>
24 
25 #include <asm/paca.h>
26 
27 /*
28  * The watchdog has a simple timer that runs on each CPU, once per timer
29  * period. This is the heartbeat.
30  *
31  * Then there are checks to see if the heartbeat has not triggered on a CPU
32  * for the panic timeout period. Currently the watchdog only supports an
33  * SMP check, so the heartbeat only turns on when we have 2 or more CPUs.
34  *
35  * This is not an NMI watchdog, but Linux uses that name for a generic
36  * watchdog in some cases, so NMI gets used in some places.
37  */
38 
39 static cpumask_t wd_cpus_enabled __read_mostly;
40 
41 static u64 wd_panic_timeout_tb __read_mostly; /* timebase ticks until panic */
42 static u64 wd_smp_panic_timeout_tb __read_mostly; /* panic other CPUs */
43 
44 static u64 wd_timer_period_ms __read_mostly;  /* interval between heartbeat */
45 
46 static DEFINE_PER_CPU(struct timer_list, wd_timer);
47 static DEFINE_PER_CPU(u64, wd_timer_tb);
48 
49 /*
50  * These are for the SMP checker. CPUs clear their pending bit in their
51  * heartbeat. If the bitmask becomes empty, the time is noted and the
52  * bitmask is refilled.
53  *
54  * All CPUs clear their bit in the pending mask every timer period.
55  * Once all have cleared, the time is noted and the bits are reset.
56  * If the time since all clear was greater than the panic timeout,
57  * we can panic with the list of stuck CPUs.
58  *
59  * This will work best with NMI IPIs for crash code so the stuck CPUs
60  * can be pulled out to get their backtraces.
61  */
62 static unsigned long __wd_smp_lock;
63 static cpumask_t wd_smp_cpus_pending;
64 static cpumask_t wd_smp_cpus_stuck;
65 static u64 wd_smp_last_reset_tb;
66 
67 static inline void wd_smp_lock(unsigned long *flags)
68 {
69 	/*
70 	 * Avoid locking layers if possible.
71 	 * This may be called from low level interrupt handlers at some
72 	 * point in future.
73 	 */
74 	raw_local_irq_save(*flags);
75 	hard_irq_disable(); /* Make it soft-NMI safe */
76 	while (unlikely(test_and_set_bit_lock(0, &__wd_smp_lock))) {
77 		raw_local_irq_restore(*flags);
78 		spin_until_cond(!test_bit(0, &__wd_smp_lock));
79 		raw_local_irq_save(*flags);
80 		hard_irq_disable();
81 	}
82 }
83 
84 static inline void wd_smp_unlock(unsigned long *flags)
85 {
86 	clear_bit_unlock(0, &__wd_smp_lock);
87 	raw_local_irq_restore(*flags);
88 }
89 
90 static void wd_lockup_ipi(struct pt_regs *regs)
91 {
92 	pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id());
93 	print_modules();
94 	print_irqtrace_events(current);
95 	if (regs)
96 		show_regs(regs);
97 	else
98 		dump_stack();
99 
100 	if (hardlockup_panic)
101 		nmi_panic(regs, "Hard LOCKUP");
102 }
103 
104 static void set_cpumask_stuck(const struct cpumask *cpumask, u64 tb)
105 {
106 	cpumask_or(&wd_smp_cpus_stuck, &wd_smp_cpus_stuck, cpumask);
107 	cpumask_andnot(&wd_smp_cpus_pending, &wd_smp_cpus_pending, cpumask);
108 	if (cpumask_empty(&wd_smp_cpus_pending)) {
109 		wd_smp_last_reset_tb = tb;
110 		cpumask_andnot(&wd_smp_cpus_pending,
111 				&wd_cpus_enabled,
112 				&wd_smp_cpus_stuck);
113 	}
114 }
115 static void set_cpu_stuck(int cpu, u64 tb)
116 {
117 	set_cpumask_stuck(cpumask_of(cpu), tb);
118 }
119 
120 static void watchdog_smp_panic(int cpu, u64 tb)
121 {
122 	unsigned long flags;
123 	int c;
124 
125 	wd_smp_lock(&flags);
126 	/* Double check some things under lock */
127 	if ((s64)(tb - wd_smp_last_reset_tb) < (s64)wd_smp_panic_timeout_tb)
128 		goto out;
129 	if (cpumask_test_cpu(cpu, &wd_smp_cpus_pending))
130 		goto out;
131 	if (cpumask_weight(&wd_smp_cpus_pending) == 0)
132 		goto out;
133 
134 	pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n",
135 			cpu, cpumask_pr_args(&wd_smp_cpus_pending));
136 
137 	/*
138 	 * Try to trigger the stuck CPUs.
139 	 */
140 	for_each_cpu(c, &wd_smp_cpus_pending) {
141 		if (c == cpu)
142 			continue;
143 		smp_send_nmi_ipi(c, wd_lockup_ipi, 1000000);
144 	}
145 	smp_flush_nmi_ipi(1000000);
146 
147 	/* Take the stuck CPUs out of the watch group */
148 	set_cpumask_stuck(&wd_smp_cpus_pending, tb);
149 
150 	wd_smp_unlock(&flags);
151 
152 	printk_safe_flush();
153 	/*
154 	 * printk_safe_flush() seems to require another print
155 	 * before anything actually goes out to console.
156 	 */
157 	if (sysctl_hardlockup_all_cpu_backtrace)
158 		trigger_allbutself_cpu_backtrace();
159 
160 	if (hardlockup_panic)
161 		nmi_panic(NULL, "Hard LOCKUP");
162 
163 	return;
164 
165 out:
166 	wd_smp_unlock(&flags);
167 }
168 
169 static void wd_smp_clear_cpu_pending(int cpu, u64 tb)
170 {
171 	if (!cpumask_test_cpu(cpu, &wd_smp_cpus_pending)) {
172 		if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) {
173 			unsigned long flags;
174 
175 			pr_emerg("Watchdog CPU:%d became unstuck\n", cpu);
176 			wd_smp_lock(&flags);
177 			cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck);
178 			wd_smp_unlock(&flags);
179 		}
180 		return;
181 	}
182 	cpumask_clear_cpu(cpu, &wd_smp_cpus_pending);
183 	if (cpumask_empty(&wd_smp_cpus_pending)) {
184 		unsigned long flags;
185 
186 		wd_smp_lock(&flags);
187 		if (cpumask_empty(&wd_smp_cpus_pending)) {
188 			wd_smp_last_reset_tb = tb;
189 			cpumask_andnot(&wd_smp_cpus_pending,
190 					&wd_cpus_enabled,
191 					&wd_smp_cpus_stuck);
192 		}
193 		wd_smp_unlock(&flags);
194 	}
195 }
196 
197 static void watchdog_timer_interrupt(int cpu)
198 {
199 	u64 tb = get_tb();
200 
201 	per_cpu(wd_timer_tb, cpu) = tb;
202 
203 	wd_smp_clear_cpu_pending(cpu, tb);
204 
205 	if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb)
206 		watchdog_smp_panic(cpu, tb);
207 }
208 
209 void soft_nmi_interrupt(struct pt_regs *regs)
210 {
211 	unsigned long flags;
212 	int cpu = raw_smp_processor_id();
213 	u64 tb;
214 
215 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
216 		return;
217 
218 	nmi_enter();
219 
220 	__this_cpu_inc(irq_stat.soft_nmi_irqs);
221 
222 	tb = get_tb();
223 	if (tb - per_cpu(wd_timer_tb, cpu) >= wd_panic_timeout_tb) {
224 		per_cpu(wd_timer_tb, cpu) = tb;
225 
226 		wd_smp_lock(&flags);
227 		if (cpumask_test_cpu(cpu, &wd_smp_cpus_stuck)) {
228 			wd_smp_unlock(&flags);
229 			goto out;
230 		}
231 		set_cpu_stuck(cpu, tb);
232 
233 		pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu);
234 		print_modules();
235 		print_irqtrace_events(current);
236 		if (regs)
237 			show_regs(regs);
238 		else
239 			dump_stack();
240 
241 		wd_smp_unlock(&flags);
242 
243 		if (sysctl_hardlockup_all_cpu_backtrace)
244 			trigger_allbutself_cpu_backtrace();
245 
246 		if (hardlockup_panic)
247 			nmi_panic(regs, "Hard LOCKUP");
248 	}
249 	if (wd_panic_timeout_tb < 0x7fffffff)
250 		mtspr(SPRN_DEC, wd_panic_timeout_tb);
251 
252 out:
253 	nmi_exit();
254 }
255 
256 static void wd_timer_reset(unsigned int cpu, struct timer_list *t)
257 {
258 	t->expires = jiffies + msecs_to_jiffies(wd_timer_period_ms);
259 	if (wd_timer_period_ms > 1000)
260 		t->expires = __round_jiffies_up(t->expires, cpu);
261 	add_timer_on(t, cpu);
262 }
263 
264 static void wd_timer_fn(unsigned long data)
265 {
266 	struct timer_list *t = this_cpu_ptr(&wd_timer);
267 	int cpu = smp_processor_id();
268 
269 	watchdog_timer_interrupt(cpu);
270 
271 	wd_timer_reset(cpu, t);
272 }
273 
274 void arch_touch_nmi_watchdog(void)
275 {
276 	unsigned long ticks = tb_ticks_per_usec * wd_timer_period_ms * 1000;
277 	int cpu = smp_processor_id();
278 
279 	if (get_tb() - per_cpu(wd_timer_tb, cpu) >= ticks)
280 		watchdog_timer_interrupt(cpu);
281 }
282 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
283 
284 static void start_watchdog_timer_on(unsigned int cpu)
285 {
286 	struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
287 
288 	per_cpu(wd_timer_tb, cpu) = get_tb();
289 
290 	setup_pinned_timer(t, wd_timer_fn, 0);
291 	wd_timer_reset(cpu, t);
292 }
293 
294 static void stop_watchdog_timer_on(unsigned int cpu)
295 {
296 	struct timer_list *t = per_cpu_ptr(&wd_timer, cpu);
297 
298 	del_timer_sync(t);
299 }
300 
301 static int start_wd_on_cpu(unsigned int cpu)
302 {
303 	unsigned long flags;
304 
305 	if (cpumask_test_cpu(cpu, &wd_cpus_enabled)) {
306 		WARN_ON(1);
307 		return 0;
308 	}
309 
310 	if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
311 		return 0;
312 
313 	if (watchdog_suspended)
314 		return 0;
315 
316 	if (!cpumask_test_cpu(cpu, &watchdog_cpumask))
317 		return 0;
318 
319 	wd_smp_lock(&flags);
320 	cpumask_set_cpu(cpu, &wd_cpus_enabled);
321 	if (cpumask_weight(&wd_cpus_enabled) == 1) {
322 		cpumask_set_cpu(cpu, &wd_smp_cpus_pending);
323 		wd_smp_last_reset_tb = get_tb();
324 	}
325 	wd_smp_unlock(&flags);
326 
327 	start_watchdog_timer_on(cpu);
328 
329 	return 0;
330 }
331 
332 static int stop_wd_on_cpu(unsigned int cpu)
333 {
334 	unsigned long flags;
335 
336 	if (!cpumask_test_cpu(cpu, &wd_cpus_enabled))
337 		return 0; /* Can happen in CPU unplug case */
338 
339 	stop_watchdog_timer_on(cpu);
340 
341 	wd_smp_lock(&flags);
342 	cpumask_clear_cpu(cpu, &wd_cpus_enabled);
343 	wd_smp_unlock(&flags);
344 
345 	wd_smp_clear_cpu_pending(cpu, get_tb());
346 
347 	return 0;
348 }
349 
350 static void watchdog_calc_timeouts(void)
351 {
352 	wd_panic_timeout_tb = watchdog_thresh * ppc_tb_freq;
353 
354 	/* Have the SMP detector trigger a bit later */
355 	wd_smp_panic_timeout_tb = wd_panic_timeout_tb * 3 / 2;
356 
357 	/* 2/5 is the factor that the perf based detector uses */
358 	wd_timer_period_ms = watchdog_thresh * 1000 * 2 / 5;
359 }
360 
361 void watchdog_nmi_reconfigure(void)
362 {
363 	int cpu;
364 
365 	watchdog_calc_timeouts();
366 
367 	for_each_cpu(cpu, &wd_cpus_enabled)
368 		stop_wd_on_cpu(cpu);
369 
370 	for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask)
371 		start_wd_on_cpu(cpu);
372 }
373 
374 /*
375  * This runs after lockup_detector_init() which sets up watchdog_cpumask.
376  */
377 static int __init powerpc_watchdog_init(void)
378 {
379 	int err;
380 
381 	watchdog_calc_timeouts();
382 
383 	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/watchdog:online",
384 				start_wd_on_cpu, stop_wd_on_cpu);
385 	if (err < 0)
386 		pr_warn("Watchdog could not be initialized");
387 
388 	return 0;
389 }
390 arch_initcall(powerpc_watchdog_init);
391 
392 static void handle_backtrace_ipi(struct pt_regs *regs)
393 {
394 	nmi_cpu_backtrace(regs);
395 }
396 
397 static void raise_backtrace_ipi(cpumask_t *mask)
398 {
399 	unsigned int cpu;
400 
401 	for_each_cpu(cpu, mask) {
402 		if (cpu == smp_processor_id())
403 			handle_backtrace_ipi(NULL);
404 		else
405 			smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000);
406 	}
407 }
408 
409 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
410 {
411 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi);
412 }
413